SSC CHSL Model Paper 20

SP of 12 apples = 100 paise
SP of 1 apple $=\frac{100}{12}$
CP of 1 apple, since the man loses 20% $=\frac{100}{12}\times 1.25$
To gain 20%, the man should sell at a new price of
$\mathrm{SP}=\frac{100}{12}\times 1.25\times 1.2$ $=12.5\mathrm{paise}$
Thus in 100 paise, apples sold $=\frac{100}{12.5}=8$
Hence, 8 apples can be purchased for Rs. 1 to gain 20%